Global command interface for a hybrid display

ABSTRACT

A hybrid display includes a first display having a first interface and a second display having a second interface. A third interface is configured to receive a first command that includes a first value indicating a modification of pixels in the hybrid display. A finite state machine is configured to translate the first value to a second value indicating a modification of pixels in the first display and a third value indicating a modification of pixels in the second display. The first interface transmits a second command including the second value to the first interface and a third command including the third value to the second interface. The first and second commands are transmitted at times determined by a relative delay between the first display and the second display.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to display systems and moreparticularly to interfaces to display systems.

BACKGROUND

Immersive virtual reality (VR) and augmented reality (AR) systemstypically utilize a head mounted display (HMD) device that presentsstereoscopic imagery to the user so as to give a sense of presence in athree-dimensional (3D) scene. For example, a typical HMD device isdesigned to produce a stereoscopic image over a field-of-view thatapproaches or is equal to the field-of-view of a human eye, which isapproximately 180°. Conventional HMD devices implement either a singleflat display that is separated into two independent display regions, onefor the left eye and one for the right eye of the user, or a pair ofindependent flat displays, one for each eye of the user. Theconventional HMD device further includes a circular lens for each eye soas to focus the entire image of the display into the user's eye.

The human eye is able to differentiate between adjacent features of animage to an eye-limiting resolution of approximately 1 arcmin/pixel,which corresponds to a pixel density of approximately 60 pixels/degree.However, the human eye is only able to perceive features at eye-limitingresolution within an area of focus of approximately 60° from a center offocus. Features outside of the area of focus (e.g., at angles between60° and 180°) are perceived with peripheral vision at a much lowerresolution. The cost and complexity of an HMD is significantly andunnecessarily increased if the display is implemented with a sufficientpixel density to provide eye-limiting resolution of over the entire 180°field-of-view. Conventional HMD devices are therefore designed tobalance the competing demands for high resolution and lowcost/complexity by using displays that have a pixel density of 10-20pixels/degree.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be better understood by, and its numerousfeatures and advantages made apparent to, those skilled in the art byreferencing the accompanying drawings. The use of the same referencesymbols in different drawings indicates similar or identical items.

FIG. 1 illustrates a display system that includes an electronic deviceconfigured to provide AR or VR functionality via a hybrid display inaccordance with at least one embodiment of the present disclosure.

FIG. 2 illustrates an example cross-section view of the electronicdevice as mounted on the head of a user in accordance with at least oneembodiment of the present disclosure.

FIG. 3 is a block diagram of a processing system that is used togenerate a display imagery using a hybrid display that includes highresolution and low-resolution displays in accordance with at least oneembodiment of the present disclosure.

FIG. 4 is a block diagram of a display system including a globalinterface that implements a finite state machine in accordance with atleast one embodiment of the present disclosure.

FIG. 5 illustrates VSYNC signals utilized by a high-resolution displayand a low-resolution display that form a hybrid display in accordancewith at least one embodiment of the present disclosure.

FIG. 6 is a block diagram of a hybrid display including a low-resolutiondisplay and a high-resolution display in accordance with at least oneembodiment of the present disclosure.

FIG. 7 is an XY chromaticity diagram that indicates a color gamut of ahigh-resolution display and a color gamut of a low-resolution display inaccordance with at least one embodiment of the present disclosure.

FIG. 8 is a flow diagram of a method of providing global commands tointerfaces of a high-resolution display and a low-resolution display ina hybrid display in accordance with at least one embodiment of thepresent disclosure.

DETAILED DESCRIPTION

The following description is intended to convey a thorough understandingof the present disclosure by providing a number of specific embodimentsand details involving imagery capture and display systems. It isunderstood, however, that the present disclosure is not limited to thesespecific embodiments and details, which are examples only, and the scopeof the disclosure is accordingly intended to be limited only by thefollowing claims and equivalents thereof. It is further understood thatone possessing ordinary skill in the art, in light of known systems andmethods, would appreciate the use of the disclosure for its intendedpurposes and benefits in any number of alternative embodiments,depending upon specific design and other needs.

FIGS. 1-8 illustrate embodiments of a hybrid display that combines alow-resolution display (e.g., a display constructed of pixels that havea pixel size of approximately 60 μm) with a high-resolution display(e.g. a semiconductor micro display constructed of pixels that have apixel size of approximately 2 μm or less). For example, an HMD mayinclude two high-resolution displays for displaying a portion of animage in the areas of focus of the left and right eyes of the user ofthe HMD. The hybrid display also includes two low-resolution displaysfor displaying a portion of the image that falls outside the areas offocus of the left and right eyes of the user. The high andlow-resolution displays may be overlaid with each other or thelow-resolution display may be formed in a region that wraps around orencompasses the outer boundary of the high-resolution display.Additional optical elements may be used to combine and focus lightemitted by the pixels in the high-resolution and low-resolution displayson to the user's eyes.

Conventional high-resolution displays and low-resolution displays arecontrolled using different interfaces. For example, the interface to aconventional high-resolution display may be implemented as aninter-integrated circuit (I²C) and the interface to a conventionallow-resolution display may be implemented as a Mobile Industry ProcessorInterface (MIPI), an embedded display port (eDP) interface, or a mobiledisplay digital interface (MDDI). The control path speed for an I²Cinterface is on the order of hundreds of kilohertz (kHz) and the controlpath speed for a MIPI (or other low-resolution display) interface is onthe order of tens of megahertz (MHz). Furthermore, the packet overheadin data packets transmitted by an I²C interface is larger than thepacket overhead in data packets transmitted by a MIPI interface. Thedifferent control path speeds and packet overheads introduce timingdifferences between the two interfaces that can generate noticeablevisual artifacts such as flicker in response to global commands thataffect pixels in both the high-resolution display and the low-resolutiondisplay. For example, a dimming algorithm can modify the brightness ofthe image produced by the display by transmitting (via the respectiveinterfaces) global dimming commands to the high-resolution andlow-resolution displays. The different control path speeds and packetoverheads result in different values of the lag between transmission ofthe global command to the displays via the corresponding interfaces andthe resulting change in the pixel values. The relative timing delaysproduced by the different values of the lag may generate flicker in thecombined image produced by the high-resolution display and thelow-resolution display. The flicker may be exacerbated by differentcolor matrices that map the brightness indicated by the global commandto different values of the brightness produced by the high resolutionand low-resolution displays.

The visual artifacts produced by a hybrid display in response toreceiving a global command may be reduced by translating the globalcommand to interface-specific commands that are understood bycorresponding interfaces to the high-resolution display and thelow-resolution display. The interface-specific commands include valuesthat represent one or more characteristics of the images. The differentvalues in the interface-specific commands are generated from acorresponding value in the global command based on different physicalproperties of the high-resolution display and the low-resolutiondisplay. For example, a global command may be issued to reduce thebrightness of an image produced by the hybrid display by a predeterminedamount that is represented by a change in a value of the luma for eachpixel. The luma values are stored in one or more registers associatedwith the high-resolution display and the low-resolution display. Thestored values are used to control a bias current or voltage that isapplied to pixels in response to input signals provided by theinterfaces to the high-resolution display and the low-resolutiondisplay. The bias currents or voltages applied to the pixels in thedifferent displays, as well as the colors produced by the pixels inresponse to the applied bias current or voltage, are typically differentdue to different physical properties of the high-resolution display andthe low-resolution display. The values of the luma indicated in theglobal command may therefore be translated to interface-specific valuesbased on the physical properties of the displays. For example, a finitestate machine may receive the global command and selectively modify theluma value (or change in the luma value) indicated in the global commandbased on different color matrices that represent the relationshipbetween a value of luma and corresponding RGB values that define thecolors displayed by the high-resolution display and the low-resolutiondisplay. The finite state machine modifies the luma values so that thechange in brightness perceived by the user is substantially the same forthe high-resolution display and the low-resolution display. The finitestate machine may also translate other global command values such asvalues that indicate a chroma that controls the bias currents orvoltages applied to pixels in response to input signals representativeof chroma, color matrices that are used to transform luma and chroma toRGB values used by the displays, gamma values that determine a power lawrelationship between an input value of luma and a gamma-corrected valueof luma used for encoding, color coordinates, a color gamut, and thelike.

The global command interface may then provide the interface-specificcommands (including the translated global command values) to thehigh-resolution display interface and the low-resolution displayinterface. To avoid flickering, the finite state machine timesynchronizes the interface-specific commands so that they are providedto the different interfaces at substantially the same time. For example,the finite state machine may provide the interface-specific commands tofirst-in-first out (FIFO) buffers at times that are offset by values ofrelative delays between signals indicating a refresh interval and ablanking interval for the high-resolution display and the low-resolutiondisplay. The values in the FIFO buffers are then shifted into theappropriate registers during the synchronized blanking intervals. Someembodiments of the offset may be determined based on the amount ofoverhead or data in the packets transmitted over the differentinterfaces. The finite state machine may also configure timingparameters of the high-resolution display interface and thelow-resolution display interface using interface-specific commands.Examples of timing parameters include parameters that specify timing ofa horizontal synchronization signal that separates scan lines in thedisplays, a vertical synchronization signal that separates fields in thedisplays, pixel scan directions, a blanking interval during which nodata is transmitted, and the like.

FIG. 1 illustrates a display system 100 that includes an electronicdevice 105 configured to provide AR or VR functionality via a hybriddisplay in accordance with at least one embodiment of the presentdisclosure. The illustrated embodiment of the electronic device 105 caninclude a portable user device, such as head mounted display (HMD), atablet computer, computing-enabled cellular phone (e.g., a“smartphone”), a notebook computer, a personal digital assistant (PDA),a gaming console system, and the like. In other embodiments, theelectronic device 105 can include a fixture device, such as medicalimaging equipment, a security imaging sensor system, an industrial robotcontrol system, a drone control system, and the like. For ease ofillustration, the electronic device 105 is generally described herein inthe example context of an HMD system; however, the electronic device 105is not limited to these example implementations.

A back plan view of an example implementation of the electronic device105 in an HMD form factor in accordance with at least one embodiment ofthe present disclosure is shown in FIG. 1. The electronic device 105 maybe implemented in other form factors, such as a smart phone form factor,tablet form factor, a medical imaging device form factor, and the like,which implement configurations analogous to those illustrated. Asillustrated by the back plan view, the electronic device 105 can includea face gasket 110 mounted on a surface 115 for securing the electronicdevice 105 to the face of the user (along with the use of straps or aharness).

The electronic device 105 includes a hybrid display 120 that is used togenerate images such as VR images or AR images that are provided to theuser. The hybrid display 120 is divided into two substantially identicalportions, a right portion to provide images to the right eye of the userand a left portion to provide images to the left eye of the user. Theleft portion includes a relatively high resolution display 125 that ispositioned at the center of the field-of-view of the user and arelatively low-resolution display 130 that encompasses thehigh-resolution display 125 and provides images at larger angles withrespect to the center of the field-of-view that correspond to theregions of peripheral vision of the user. The right portion includes ahigh-resolution display 135 and a low-resolution display 140 that aresubstantially identical to the corresponding high resolution display 125and low-resolution display 130. The high-resolution displays 125, 135have a larger pixel density than the low-resolution displays 130, 140.Pixel sizes in the high-resolution displays 125, 135 are smaller thanpixel sizes in the low-resolution displays 130, 140. For example, thehigh-resolution displays 125, 135 may have a pixel size of less than 5μm (such as a pixel size of 2 μm) and the low-resolution displays 130,140 may have a pixel size in the range of 10-100 μm, such as a pixelsize of 60 μm.

The high-resolution displays 125, 135 are controlled using signalsprovided by one or more high-resolution interfaces 145. Some embodimentsof the high-resolution interfaces 145 are implemented as aninter-integrated circuit (I²C) interface that has a control path speedon the order of hundreds of kilohertz (kHz). The low-resolution displays130, 140 are controlled using signals provided by one or morelow-resolution interfaces 150. The low-resolution interfaces 150 may beimplemented as a Mobile Industry Processor Interface (MIPI), an embeddeddisplay port (eDP) interface, or a mobile display digital interface(MDDI). The control path speed for a MIPI (or other low-resolution)interface is on the order of tens of megahertz (MHz). In someembodiments, the packet overhead in data packets transmitted by an I²Cinterface such as the high-resolution displays 125, 135 is larger thanthe packet overhead in data packets transmitted by a MIPI, eDP, or MDDIinterface such as the low-resolution displays 130, 140.

The display system 100 includes a global interface 155 for receivingglobal commands to control or modify images displayed by thehigh-resolution displays 125, 135 and the low-resolution displays 130,140 in the hybrid display 120. As used herein, the term “global command”refers to a command that is used to control or modify characteristics ofthe light generated by one or more pixels in the high-resolutiondisplays 125, 135 and one or more pixels in the low-resolution displays130, 140. For example, the global interface 155 may receive a globalcommand to dim the light generated by the high-resolution displays 125,135 and the low-resolution displays 130, 140 by changing the brightnessof the pixels in the hybrid display 120. Global commands indicate values(or modifications to values) of characteristics of the light generatedby the pixels that are intended to cause predetermined modifications inobserved images produced by the pixels in the hybrid display 120.However, the different physical characteristics of the high-resolutiondisplays 125, 135 and the low-resolution displays 130, 140 may cause thepixels in these displays to produce light having differentcharacteristics in response to the same global command. Moreover, timingdifferences between the high-resolution interface 145 and thelow-resolution interface 150 may cause the modifications to occur atdifferent times in the high-resolution displays 125, 135 and thelow-resolution displays 130, 140.

In order to reduce the flicker caused by timing differences or differentphysical characteristics, some embodiments of the global interface 155perform translation and synchronization operations on the global commandto produce interface-specific commands that are transmitted to thehigh-resolution interface 145 and the low-resolution interface 150. Forexample, the global interface 155 may receive a global command thatincludes one or more values indicating a modification of signalsprovided to pixels in the hybrid display 120. The global interface 155may then translate the one or more values into corresponding valuesindicating modifications of the signals provided to the pixels in thehigh-resolution displays 125, 135 and the low-resolution displays 130,140 based on the different physical properties or characteristics of thedisplays 125, 130, 135, 140. The global interface 155 can accessinformation indicating timing delays (or a relative timing delay)between control signals used by the high-resolution displays 125, 135and the low-resolution displays 130, 140. The global interface 155 usesthe timing delays (or relative timing delay) to synchronize theinterface-specific commands, e.g., by transmitting commands to thehigh-resolution interface 145 and the low-resolution interface 150 attimes determined by the timing delays (or relative timing delay) so thatinterface-specific commands including the translated values are providedat substantially the same time. Some embodiments of the global interface155 modify timing of a vertical synchronization signal (VSYNC) of one ormore of the interfaces 145, 150 to align the vertical synchronizationsignals of the interfaces 145, 150, as discussed herein.

FIG. 2 illustrates an example cross-section view 200 of the electronicdevice 105 as mounted on the head 202 of a user in accordance with atleast one embodiment of the present disclosure. As illustrated, theelectronic device 105 includes a housing 204 that includes thehigh-resolution displays 125, 135 and the low-resolution displays 130,140 that form the hybrid display 120. The electronic device 105 alsoincludes eyepiece lenses 206 and 208 disposed in corresponding aperturesor other openings in the user-facing surface 115 of the housing 204. Theelectronic device 105 further includes the hybrid display 120 disposeddistal to the eyepiece lenses 206 and 208 within the housing 204. Theeyepiece lens 206 is aligned with the high-resolution display 125 andthe low-resolution display 130 shown in FIG. 1, while the eyepiece lens208 is aligned with the high-resolution display 135 and thelow-resolution display 140 shown in FIG. 1.

In a stereoscopic display mode, imagery may be displayed by thecombination of the high-resolution display 125 and the low-resolutiondisplay 130 and viewed by the user's left eye via the eyepiece lens 206.Imagery may be concurrently displayed by the combination of thehigh-resolution display 135 and the low-resolution display 140 andviewed by the user's right eye via the eyepiece lens 208. Someembodiments of the high-resolution displays 125, 135 may be fabricatedto include a bezel (not shown in FIG. 2) that encompasses an outer edgeof the high-resolution displays 125, 135. The lenses 206, 208 or otheroptical devices may therefore be used to combine the images produced bythe displays 125, 130, 135, 140 so that bezels around thehigh-resolution displays 125, 135 are not seen by the user. Instead,lenses 206, 208 merge the images to appear continuous across boundariesbetween the displays 125, 130, 135, 140.

In some embodiments, some or all of the electronic components thatcontrol and support the operation of the hybrid display 120 and othercomponents of the electronic device 105 may be implemented within thehousing 204. For example, the housing 204 may incorporate a globalinterface 210, high-resolution interfaces 212 and 214, andlow-resolution interfaces 216 and 218. As discussed herein, the globalinterface 210 receives global commands 220 and translates orsynchronizes the commands to form interface-specific commands that areprovided to the interfaces 212, 214, 216, 218. Although the components210, 212, 214, 216, 218 are depicted as monolithic blocks for ease ofillustration, it will be appreciated that these electronic componentsmay be implemented either as a single package or component, or as a setof discrete, interconnected electronic components. Moreover, in someembodiments, some or all of these electronic components may beimplemented remote to the housing 204. To illustrate, the processingcomponents of the display system may be implemented in a separatedevice, such as a tablet computer, notebook computer, desktop computer,compute-enabled cellphone, and which is connected to a HMD incorporatingthe hybrid display 120 via one or more wireless or wired connections.

FIG. 3 is a block diagram of a processing system 300 that is used togenerate display imagery using a hybrid display that includes highresolution and low-resolution displays in accordance with at least oneembodiment of the present disclosure. The processing system 300 includesat least one processing unit 305 that generates signals representativeof images for display, such as stereoscopic images for display to theleft eye and the right eye of a user. The processing unit 305 may beimplemented as a central processing unit (CPU), a graphics processingunit (GPU), one or more processor cores implemented in the CPU or GPU,or other processing device. In the illustrated embodiment, theprocessing unit 305 generates signals representative of images that areto be displayed using a hybrid display formed of four separate displays:a high-resolution display 310 and a low-resolution display 315 that arecombined to provide images to a left eye of a user and a high-resolutiondisplay 320 and a low-resolution display 325 that are combined toprovide images to a right eye of the user. Thus, the processing unit 305includes four ports 330, 331, 332, 333 (referred to collectively as “theports 330-333”) for providing signals associated with the correspondingdisplays 310, 315, 320, 325. The ports 330-333 may be physical ports orlogical ports.

The processing system 300 includes an interface 335 that receivessignals from the processing unit 305 at corresponding ports 340, 341,342, 343 (referred to collectively as “the ports 340-343”). The ports340-343 may be physical ports or logical ports. The interface 335combines the signals received at the ports 340-343 so that they may betransmitted over a single line such as a fiber-optic cable 345 that iscoupled to a port 346. Some embodiments of the interface 335 include aprocessing unit and a transceiver that are configured to perform amultiplexing operation to combine the signals received at the ports340-343 and transmit the multiplexed signal over the fiber-optic cable345.

The fiber-optic cable 345 is also connected to a port 347 of aninterface 350. Some embodiments of the interface 350 include a globalinterface such as the global interface 155 shown in FIG. 1, one or morehigh-resolution interfaces such as the high-resolution interface 145shown in FIG. 1, and one or more low-resolution interfaces such as thelow-resolution interface 150 shown in FIG. 1. The interface 350 maytherefore receive signals including global commands generated by theprocessing unit 305. As discussed herein, the global commands may betranslated into interface-specific commands, which may be synchronizedto reduce visual artifacts in the images displayed by the displays 310,315, 320, 325.

FIG. 4 is a block diagram of a display system 400 including a globalcommand interface 405 that implements a finite state machine 410 inaccordance with at least one embodiment of the present disclosure.Although the finite state machine 410 is depicted as an integralcomponent of the global command interface 405, some embodiments mayimplement the finite state machine 410 external to the global commandinterface 405. The global command interface 405 is configured to receivesignals 415 including global commands that are used to control theoutput of the displays 420, 421, 422, 423 (referred to collectively as“the displays 420-423”), which include high-resolution displays 420, 422and low-resolution displays 421, 423. In the interest of clarity, thedisplays 420-423 are depicted side-by-side in FIG. 4. However, thedisplays 420-423 are intended to implement a hybrid display such as thehybrid display 120 shown in FIG. 1. For example, the high-resolutiondisplay 420 may be combined or overlaid with the low-resolution display421 to provide images to the left eye of a user. The high-resolutiondisplay 422 may be combined or overlaid with the low-resolution display423 to provide images to the right eye of a user.

Each of the displays 420-423 receives data and control signals via acorresponding one of interfaces 425, 426, 427, 428 (collectivelyreferred to as “the interfaces 425-428”). In the illustrated embodiment,the high-resolution displays 420, 422 are controlled by signals receivedfrom the high-resolution interfaces 425, 427 and the low-resolutiondisplays 421, 423 are controlled by signals received from thelow-resolution interfaces 426, 428. The interfaces 425-428 are connectedto corresponding sets of registers 430, 431, 432, 433 (collectivelyreferred to as “the register sets 430-433”) that store values that areused to determine the signals provided to the displays 420-423. Forexample, the register sets 430-433 may be used to store luma values thatare used to determine a bias current or voltage that is applied topixels in the displays 420-423 in response to input signalsrepresentative of the luma, e.g., input signals received from the globalcommand interface 405. The register sets 430-433 may also be used tostore values of chroma that control the bias currents or voltagesapplied to pixels in the displays 420-423 in response to input signalsrepresentative of chroma, values of color matrices that are used totransform luma and chroma to RGB values used by the displays 420-423,values of gamma that determine a power law relationship between an inputvalue of luma and a gamma-corrected value of luma used for encoding,values of color coordinates, or values of a color gamut. Someembodiments of the register sets 430-433 store values of timingparameters that are used to determine timing of the signals provided tothe interfaces 425-428 or transmitted by the interfaces 425-428. Forexample, the register sets 430-433 may store values that specify timingof a horizontal synchronization signal that separates scan lines in thedisplays 420-423, a vertical synchronization signal that separatesfields in the displays 420-423, pixel scan directions, a blankinginterval during which no data is transmitted from the interfaces 425-428to the corresponding displays 420-423, and the like.

The displays 420-423 are composed of pixels 435 formed of displayelements such as light emitting diodes (LEDs) or organic light emittingdiodes (OLEDs). In the interest of clarity only one of the pixels 435 isindicated by a reference numeral. The pixels 435 in the displays 420-423are selectively activated though respective column drivers 440, 441,442, 443 (collectively referred to as “the column drivers 440-443”) androw drivers 445, 446, 447, 448 (collectively referred to as “the rowdrivers 445-448”). The interfaces 425-428 provide control signals to thecorresponding column drivers 440-443 and row drivers 445-448. Forexample, the interface 425 may provide a row select indicator to the rowdriver 445 indicating a row of the display 421 based on a row positionof a received pixel row and provide pixel row data to the column driver440 representing the pixel values of the pixels in the received pixelrow. The row driver 445 and the column driver 440 then control theirrespective outputs to the display 421 based on these inputs so as toselectively activate pixels in the corresponding row of the display 421so as to display a representation of the pixel row at that row ofdisplay 421.

Global commands include values (or modifications to values) of imageparameters that are intended to produce a predetermined modifications inobserved images produced by the pixels in the displays 420-423.Conventional global commands assume that providing the same value (orthe same modification to the value) of the image parameters will producethe same modification in the observed images produced by the pixels inall of the displays 420-423. This assumption does not necessarily holdtrue in a hybrid display that includes both high-resolution displays420, 422 and low-resolution displays 421, 423 because of the differentphysical characteristics of these displays. For example, configuring theinterfaces 425-428 with a single value of luma included in a globalcommand may result in different bias currents or voltages being appliedto the pixels in the high-resolution displays 420, 422 andlow-resolution displays 421, 423, which may result in a differentobserved brightness or change in the observed brightness in thedifferent displays 420-423.

The finite state machine 410 may therefore translate the parameters inglobal commands based on the different physical characteristics of thedisplays 420-423. For example, gamma correction (or gamma encoding anddecoding) may be used to compress the number of bits needed to encode animage by taking advantage of the non-linear response of the human eye tolight in color. A power law relation between an input value (such asluminance) and an output value is set by the value of γ:V _(out) =AV _(in) ^(γ)The input value a parameter is provided by the global command and theoutput value is used to encode the parameter. However, thehigh-resolution displays 420, 422 may have a value of γ_(hi) thatdiffers from the value of γ_(lo) associate with the low-resolutiondisplays 421, 423. The finite state machine 410 may therefore translatethe global command to interface-specific commands to account for thedifferences between the gamma values used by the different displays420-423. For example, the finite state machine 410 may modify values ofγ_(hi) or γ_(lo) so that the interface-specific commands generated basedon a global command produce a predetermined modification in the observedimages produced by the pixels in all of the displays 420-423. The finitestate machine 410 may also translate the global command to correspond tothe format used by the corresponding interfaces 425-428. For example,the finite state machine 410 may transmit the format of the globalcommand to formats used by an inter-integrated circuit (I²C), a MobileIndustry Processor Interface (MIPI), an embedded display port (eDP)interface, or a mobile display digital interface (MDDI), depending onthe type of interface.

The global command interface 405 provides the interface-specificcommands to the interfaces 425-428 during blanking intervals that occurbetween the refresh periods during which the corresponding interfaces425-428 refresh the signal applied to the pixels 435 to reflect anychanges in the image. The blanking intervals are defined by a verticalsynchronization signal (VSYNC). For example, a blanking interval maybegin with the rising edge of the VSYNC signal and may end with thefalling edge of the VSYNC signal. Alternatively, the blanking intervalmay begin with the falling edge of the VSYNC signal and end with therising edge of the VSYNC signal, depending on the state of a polaritysignal. However, differences in the control path speeds of theinterfaces 425-428 and different amounts of overhead in the data packetsthat include the interface-specific commands transmitted to theinterfaces 425-428 can introduce timing delays between the VSYNC signalsso that the blanking intervals for the different interfaces 425-428 areout of synchronization.

A register 450 includes information indicating the relative timingdelays between the high-resolution interfaces 425, 427 and thelow-resolution interfaces 426, 428. The finite state machine 410 mayaccess the information in the register 450 and use this information toaccount for the timing delays when scheduling transmission of theinterface-specific commands to the interfaces 425-428. For example, thefinite state machine 410 may provide the interface-specific commands tofirst-in-first-out (FIFO) buffers 451, 452, 453, 454 (collectivelyreferred to herein as “the FIFO buffers 451-454”) at times that aredetermined based on the relative timing delay so that this informationis available to configure the interfaces 425-428 during thecorresponding blanking intervals. Configuring the interfaces 425-428 mayinclude updating or modifying timing information in the register sets430-433 using information included in the interface-specific commands.The finite state machine 410 may also use the relative timing delaysindicated by the value of the register 450 to synchronize the blankingintervals by selectively delaying one or more VSYNC signals utilized byone or more of the interfaces 425-428.

FIG. 5 illustrates VSYNC signals utilized by a high-resolution displayand a low-resolution display that form a hybrid display in accordancewith at least one embodiment of the present disclosure. The VSYNC signal505 is provided to the high-resolution display and the VSYNC signal 510is provided to the low-resolution display. In the illustratedembodiment, a falling edge of the VSYNC signals 505, 510 indicates thebeginning of a refresh interval such as the refresh interval 515. Thepixels in the displays are refreshed during the refresh interval 515based on signals provided by the corresponding interfaces and values ofconfiguration registers such as the register sets 430-433 shown in FIG.4. A rising edge of the VSYNC signals 505, 510 indicates the beginningof a blanking interval such as the blanking interval 520. No data istransmitted from the interfaces to the corresponding displays during theblanking interval 520. The blanking interval 520 may therefore be usedto update the configuration of the interfaces to the displays. Forexample, configuration information provided to the interfaces 425-428 bythe global command interface 405 shown in FIG. 4 may be used toreconfigure the interfaces 425-428 during the blanking interval 520,e.g., by storing updated or modified information in the register sets430-433.

The VSYNC signals 505, 510 are out of synchronization. In theillustrated embodiment, the VSYNC signal 505 is delayed relative to theVSYNC signal 510 by a relative delay 525. A finite state machine (suchas the finite state machine 410 shown in FIG. 4) may thereforesynchronize operation of the high-resolution and low-resolution displaysby modifying one or more of the VSYNC signals 505, 510. In theillustrated embodiment, the finite state machine determines a value ofthe relative delay 525 (e.g. by accessing the register 450 shown in FIG.4) and then delays the VSYNC signal 510 by a delay interval 535 to formthe delayed VSYNC signal 515. The interface-specific commands that aregenerated based on a global command may be used to configure thecorresponding interfaces of the high-resolution display and thelow-resolution display during the synchronized blanking intervals 540,545. Synchronizing the interface-specific commands may reduce flickercaused by applying a global command to both the high-resolution displayand the low-resolution display in a hybrid display.

FIG. 6 is a block diagram of a hybrid display 600 including alow-resolution display 605 and a high-resolution display 610 inaccordance with at least one embodiment of the present disclosure. Thelow-resolution display 605 may be used to implement some embodiments ofthe low-resolution displays 130, 140 shown in FIG. 1 and thehigh-resolution display 610 may be used to implement some embodiments ofthe high-resolution displays 125, 135 shown in FIG. 1. Pixels in thelow-resolution display 605 and the high-resolution display 610 arerefreshed in a sequence indicated by scan lines such as the scan line615 at the top of the low-resolution display 605. The arrow in the scanline 615 indicates that the pixels are refreshed from left to right.Separate scan lines in the illustrated embodiment are refreshed from topto bottom, as indicated by the dotted arrow 620. However, someembodiments of the hybrid display 600 may use other scan patternsincluding refreshing the scan lines from right to left or bottom to top.

The scan lines in the low-resolution display 605 are interrupted by scanlines in the high-resolution display 610. For example, the scan line 625in the low-resolution display 605 is interrupted by the scan line 630 inthe high-resolution display 610, before resuming as the scan line 635and the low-resolution display 605. Furthermore, the low-resolutiondisplay 605 has a lower pixel density than the high-resolution display610 and, consequently, the density of scan lines is lower in thelow-resolution display 605 than the high-resolution display 610. Forexample, there are three scan lines in the high-resolution display 610for each scan line in the low-resolution display 605.

Absence of coordination between the timing used to refresh the scanlines in the low-resolution display 605 and the high-resolution display610 may generate flicker in the resulting image, particularly whenexecuting global commands. A finite state machine associated with aglobal command interface (such as finite state machine 410 associatedwith the global command interface 405 shown in FIG. 4) may thereforegenerate, in response to receiving a global command, interface-specificcommands to configure the high and low-resolution interfaces tocoordinate the timing used to refresh the scan lines in the two displays605, 610. Some embodiments of the interface-specific commands includeinformation to configure or modify values indicating timing parameterssuch as a timing of a horizontal synchronization signal that separatesscan lines in the displays, pixel scan directions, and the like. Forexample, the interface-specific commands may include values thatconfigure the high-resolution display 610 to begin refreshing the scanline 630 at substantially the same time that the low-resolution display605 finishes refreshing the scan line 625. The low-resolution display605 may also be configured to begin refreshing the scan line 635 atsubstantially the same time that the high-resolution display 610finishes refreshing the scan line 630. Timing parameters may also beconfigured or modified so that scan lines in the high-resolution display610 are refreshed at a higher frequency than the scan lines in thelow-resolution display 605 to account for the different pixel densitiesor scan line densities. The values may be stored in registers such asthe register sets 430-433 shown in FIG. 4 during a blanking interval, asdiscussed herein.

FIG. 7 is an XY chromaticity diagram 700 that indicates a color gamut705 of a high-resolution display and a color gamut 710 of alow-resolution display in accordance with at least one embodiment of thepresent disclosure. The vertical axis indicates the y-coordinate in theXYZ color system established by the International Commission onIllumination (CIE) and the horizontal axis indicates the x-coordinate inthe XYZ color system. The values of these coordinates determine the RGBvalues of the colors that can be displayed by the correspondingdisplays. For example, the color gamut 705 may correspond to 80% of thestandard RGB (sRGB) color range and 75% of the National TelevisionSystem Committee (NTSC) standard color range. Although the XYchromaticity diagram 700 shown in FIG. 7 is depicted in black and white,persons of ordinary skill in the art should appreciate that each pointin the XY chromaticity diagram 700 corresponds to a different color withgreener colors being found in the upper left, bluer colors in the lowerleft, and redder colors to the right of the XY chromaticity diagram 700.

The different shapes of the color gamut 705 and the color gamut 710indicate that the high-resolution display and the low-resolution displayare capable of displaying different ranges (or gamuts) of colors.Consequently, a global command that indicates one or more colors (or oneor more modifications to colors) that are to be displayed by thehigh-resolution display and the low-resolution display may result indifferent colors in the observed images produced by the high-resolutiondisplay and the low-resolution display. A finite state machineassociated with a global command interface (such as finite state machine410 associated with the global command interface 405 shown in FIG. 4)may therefore translate the values in the global command tointerface-specific commands based on the color gamut 705 and the colorgamut 710. For example, the finite state machine may apply a filter tothe values in the global command to generate interface-specific commandsthat control the high-resolution display to account for the larger colorgamut 705 reproducible by the high-resolution display. Applying thefilter may reduce differences in the colors in the observed imageproduced by the high-resolution display and the low-resolution displayin response to the global command.

FIG. 8 is a flow diagram of a method 800 of providing global commands tointerfaces of a high-resolution display and a low-resolution display ina hybrid display in accordance with at least one embodiment of thepresent disclosure. The method 800 may be implemented in someembodiments of the display system 100 shown in FIG. 1, the displaysystem as shown via cross-section view 200 in FIG. 2, the processingsystem 300 shown in FIG. 3, or the display system 400 shown in FIG. 4.

At block 805, a global command interface receives a global command thatindicates values (or modifications to values) of pixels in one or morehigh-resolution displays and one or more low-resolution displays of ahybrid display. At block 810, a finite state machine associated with theglobal command interface translates the global command tointerface-specific commands. Translation of the global command to theinterface-specific commands may include modifying values of parametersthat control the displays based on the characteristics of the interfacesto the high-resolution displays and the low-resolution displays,modifying the format of the global command to correspond to the formatsused by the interfaces to the high-resolution displays and thelow-resolution displays, and the like.

At block 815, the finite state machine accesses delay information thatindicates relative timing delays between the high-resolution displaysand the low-resolution displays. For example, the delay information mayindicate a relative delay between VSYNC signals that define refreshintervals and blanking intervals for the displays. Some embodiments ofthe finite state machine access the delay information from an associatedregister. At block 820, the global command interface provides theinterface-specific commands to the interfaces for the high-resolutiondisplays and the low-resolution displays at times determined by thedelay information. For example, the global command interface may delay(or may instruct the high-resolution display interface or thelow-resolution display interface to delay) one or more of the VSYNCsignals to synchronize the blanking intervals for the differentinterfaces. The global command interface may then provide theinterface-specific commands to FIFO buffers associated with thedifferent interfaces so that they are available to configure theinterfaces during the blanking interval.

At block 825, register sets associated with the different interfaces areupdated based on the interface-specific commands. For example, values ofthe registers (or modifications to the values of the registers) may bewritten from the FIFO buffers to the corresponding register sets toreconfigure the different interfaces. Once the blanking interval ends,the updated or modified values in the register sets are used to controlthe image that is produced during the subsequent refresh interval.

Much of the inventive functionality and many of the inventive principlesdescribed above are well suited for implementation with or in integratedcircuits (ICs) such as application specific ICs (ASICs). It is expectedthat one of ordinary skill, notwithstanding possibly significant effortand many design choices motivated by, for example, available time,current technology, and economic considerations, when guided by theconcepts and principles disclosed herein will be readily capable ofgenerating such ICs with minimal experimentation. Therefore, in theinterest of brevity and minimization of any risk of obscuring theprinciples and concepts according to the present disclosure, furtherdiscussion of such software and ICs, if any, will be limited to theessentials with respect to the principles and concepts within thepreferred embodiments.

In this document, relational terms such as first and second, and thelike, may be used solely to distinguish one entity or action fromanother entity or action without necessarily requiring or implying anyactual such relationship or order between such entities or actions. Theterms “comprises,” “comprising,” or any other variation thereof, areintended to cover a non-exclusive inclusion, such that a process,method, article, or apparatus that comprises a list of elements does notinclude only those elements but may include other elements not expresslylisted or inherent to such process, method, article, or apparatus. Anelement preceded by “comprises . . . a” does not, without moreconstraints, preclude the existence of additional identical elements inthe process, method, article, or apparatus that comprises the element.The term “another”, as used herein, is defined as at least a second ormore. The terms “including” and/or “having”, as used herein, are definedas comprising. The term “coupled”, as used herein with reference toelectro-optical technology, is defined as connected, although notnecessarily directly, and not necessarily mechanically. The term“program”, as used herein, is defined as a sequence of instructionsdesigned for execution on a computer system. A “program”, or “computerprogram”, may include a subroutine, a function, a procedure, an objectmethod, an object implementation, an executable application, an applet,a servlet, a source code, an object code, a shared library/dynamic loadlibrary and/or other sequence of instructions designed for execution ona computer system.

The specification and drawings should be considered as examples only,and the scope of the disclosure is accordingly intended to be limitedonly by the following claims and equivalents thereof. Note that not allof the activities or elements described above in the general descriptionare required, that a portion of a specific activity or device may not berequired, and that one or more further activities may be performed, orelements included, in addition to those described. Still further, theorder in which activities are listed are not necessarily the order inwhich they are performed. The steps of the flowcharts depicted above canbe in any order unless specified otherwise, and steps may be eliminated,repeated, and/or added, depending on the implementation. Also, theconcepts have been described with reference to specific embodiments.However, one of ordinary skill in the art appreciates that variousmodifications and changes can be made without departing from the scopeof the present disclosure as set forth in the claims below. Accordingly,the specification and figures are to be regarded in an illustrativerather than a restrictive sense, and all such modifications are intendedto be included within the scope of the present disclosure.

Benefits, other advantages, and solutions to problems have beendescribed above with regard to specific embodiments. However, thebenefits, advantages, solutions to problems, and any feature(s) that maycause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeature of any or all the claims.

What is claimed is:
 1. A method comprising: receiving a first commandcomprising a first value indicating a modification of pixels in a hybriddisplay that comprises a first display and a second display, whereinreceiving the first command comprises receiving the first valueindicating a modification of a characteristic of an image produced bypixels in the first display and the second display; translating thefirst value to a second value indicating a modification of pixels in thefirst display and a third value indicating a modification of pixels inthe second display, wherein translating the first value to the secondvalue and the third value comprises translating the first value to asecond value indicating a modification of the characteristic of theimage produced by the pixels in the first display and a third valueindicating a modification of the characteristic of the image produced bythe pixels in the second display, wherein the modification of thecharacteristic of the image produced by the pixels in the first displayindicated by the second value is substantially the same as themodification of the characteristic of the image produced by the pixelsin the second display indicated by the third value; and transmitting asecond command comprising the second value and a third commandcomprising the third value at times determined by a relative delaybetween the first display and the second display.
 2. The method of claim1, wherein receiving the first command comprises receiving a firstcommand indicating at least one value of at least one of luma, chroma,gamma, a color matrix, and color coordinates of pixels in the hybriddisplay.
 3. The method of claim 2, wherein translating the first valueto the second and third values comprises translating the at least onevalue to second and third values of the at least one of the luma, thechroma, the gamma, the color matrix, and the color coordinates of pixelsin the first and second displays so that the modification indicated inthe first command generates predetermined modifications in observedimages produced by the first and second displays.
 4. The method of claim1, wherein receiving the first command comprises receiving a firstcommand indicating at least one value of at least one of timing of ahorizontal synchronization signal, timing of a vertical synchronizationsignal, a pixel scan direction, and a blanking interval.
 5. The methodof claim 4, wherein translating the first value to the second and thirdvalues comprises translating the at least one value to second and thirdvalues of the at least one of the timing of the horizontalsynchronization signal, the timing of the vertical synchronizationsignal, the pixel scan direction, and the blanking interval based onrelative positions and pixel densities of the first and second displays.6. The method of claim 1, wherein transmitting the second command andthe third command comprises synchronizing transmission of the second andthird commands based on the relative delay such that modifications to anobserved image produced by the first and second displays occur atsubstantially the same time in response to the second and thirdcommands, respectively.
 7. The method of claim 6, wherein synchronizingtransmission of the second and third commands further comprisesdelaying, by the relative delay, at least one vertical synchronizationsignal that defines a blanking interval for at least one of the firstand second displays.
 8. The method of claim 1, further comprising:displaying imagery at the first display and the second display based onthe second and third commands.
 9. An apparatus comprising: a hybriddisplay comprising a first display having a first interface and a seconddisplay having a second interface; a third interface to receive a firstcommand comprising a first value indicating a modification of acharacteristic of an image produced by pixels in the first display andthe second display; and a finite state machine to translate the firstvalue to a second value indicating a modification of the characteristicof the image produced by the pixels in the first display and a thirdvalue indicating a modification of the characteristic of the imageproduced by the pixels in the second display, wherein the firstinterface transmits a second command comprising the second value to thefirst interface and a third command comprising the third value to thesecond interface at times determined by a relative delay between thefirst display and the second display, wherein the modification of thecharacteristic of the image produced by the pixels in the first displayindicated by the second value is substantially the same as themodification of the characteristic of the image produced by the pixelsin the second display indicated by the third value.
 10. The apparatus ofclaim 9, wherein the third interface is to receive a first commandindicating at least one value of at least one of luma, chroma, gamma, acolor matrix, and color coordinates of pixels in the hybrid display. 11.The apparatus of claim 10, wherein the finite state machine is totranslate the at least one value to second and third values of the atleast one of the luma, the chroma, the gamma, the color matrix, and thecolor coordinates of pixels in the first and second displays so that themodification indicated in the first command generates predeterminedmodifications in observed images produced by the first and seconddisplays.
 12. The apparatus of claim 9, wherein the third interface isto receive a first command indicating at least one value of at least oneof timing of a horizontal synchronization signal, timing of a verticalsynchronization signal, a pixel scan direction, and a blanking interval.13. The apparatus of claim 12, wherein the finite state machine is totranslate the at least one value to second and third values of the atleast one of the timing of the horizontal synchronization signal, thetiming of the vertical synchronization signal, the pixel scan direction,and the blanking interval based on relative positions and pixeldensities of the first and second displays.
 14. The apparatus of claim9, further comprising: a first register to store a value indicating therelative delay, and wherein the finite state machine is to access thevalue in the first register.
 15. The apparatus of claim 14, wherein thethird interface is to synchronize transmission of the second and thirdcommands based on the relative delay such that modifications to anobserved image produced by the first and second displays occur atsubstantially the same time in response to the second and thirdcommands, respectively.
 16. The apparatus of claim 15, wherein the thirdinterface is to synchronize transmission of the second and thirdcommands by delaying, by the relative delay, at least one verticalsynchronization signal that defines a blanking interval for at least oneof the first and second displays.
 17. A head mounted display systemcomprising: a hybrid display comprising two first displays havingcorresponding first interfaces and two second displays havingcorresponding second interfaces, wherein a first combination of a firstdisplay and a second display is to provide images to a left eye and asecond combination of a first display and a second display is to provideimages to a right eye; a third interface to receive a first commandcomprising a first value indicating a modification of characteristics ofimages produced by pixels in the first display and the second display;and a finite state machine to translate the first value to second valuesindicating modification of the characteristics of the images produced bythe pixels in the first displays and third values indicatingmodification of the characteristics of the images produced by the pixelsin the second displays, wherein the first interface transmits secondcommands comprising the second values to the first interfaces and thirdcommands comprising the third values to the second interfaces at timesdetermined by a relative delay between the first displays and the seconddisplays, and wherein the modification of the characteristics of theimages produced by the pixels in the first displays indicated by thesecond value are substantially the same as the modification of thecharacteristics of the images produced by the pixels in the seconddisplays indicated by the third value.
 18. The head mounted displaysystem of claim 17, wherein the finite state machine is to translate thefirst value to second and third values of at least one of luma, chroma,gamma, a color matrix, and color coordinates of pixels in the first andsecond displays so that the modification indicated in the first commandgenerates predetermined modifications in observed images produced by thefirst and second displays.
 19. The head mounted display system of claim17, wherein the finite state machine is to translate the first value tosecond and third values of at least one of timing of a horizontalsynchronization signal, timing of a vertical synchronization signal, apixel scan direction, and a blanking interval based on relativepositions and pixel densities of the first and second displays.
 20. Thehead mounted display system of claim 17, wherein the third interface isto synchronize transmission of the second and third commands based onthe relative delay such that modifications to an observed image producedby the first and second displays occur at substantially the same time inresponse to the second and third commands, respectively.